|Rajasekaran, Kanniah - Rajah|
Submitted to: In Vitro Cellular And Developmental Biology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/1/2003
Publication Date: 3/1/2004
Citation: Sakhanokho, H.F., Zipf, A., Rajasekaran, K., Saha, S., Sharma, G.C., Chee, P.W. 2004. Somatic embryo initiation and germination in diploid cotton (Gossypium arboreum L.). In Vitro Cellular and Developmental Biology-Plant. 40:177-181. Interpretive Summary: While species of cotton play a key role as a valuable gene pool in cotton improvement for agronomic and fiber traits through molecular breeding techniques, they offer a better opportunity than the commercially cultivated Upland cottons to study gene structure and function through gene knockout experiments because of the small genome size. A reliable regeneration system, whereby mature plants could be obtained from competent cell and tissue cultures, is required to achieve this goal. Our laboratory has been successful in obtaining "seed-like" embryos from cell cultures of one of the wild species, but the germination of embryos into plants was low. This manuscript describes several factors that were applied to embryos to enhance the germination percentage. In combinations with other culture conditions, a simple desiccation treatment to embryos significantly increased the germination rate and subsequent survival in soil. The principal users of information will be scientists involved in related transgenic research and those in the biotechnology industry.
Technical Abstract: The diploid cotton species can constitute not only a valuable gene pool for the more agronomically desirable cultivated tetraploid cultivars but also offer better opportunities to study gene structure and function through gene knockouts. In order to exploit these advantages, a regeneration system is required to achieve these transformation-based goals. Carbohydrate source and concentration levels were evaluated to improve somatic embryo (SE) production and desiccation treatments to improve the conversion efficiency of SEs to plants in a diploid G. arboreum accession, A2-9 (PI-529712). Neither a 5-day desiccation treatment of embryogenic callus previously cultured in liquid medium nor filter paper insertion improved the numbers of SEs induced or their conversion to plantlets. However, better results were achieved with an MS/sucrose-based medium M2 [0.04 M sucrose, 0.3 uM NAA] that produced 219 embryos g/L, and close to 11% of these embryos germinated into plantlets. In a second experiment, when immature G. arboreum SEs induced on M1 [0.2 M glucose, 2.6 uM NAA, and 0.2 uM kinetin] medium underwent a 3-day desiccation treatment, 49% of these immature SEs were converted to plantlets after a 4-week period on M2 medium. These improved results can help pave the way for the future genetic transformation and associated gene structure and function studies utilizing G. arboreum. These results, in particular the 3-day desiccation treatment, can also be incorporated into regeneration protocols to help improve the regeneration efficiency of other Gossypium species.